In the 50th spring annual meeting of the Chemical Society of Japan, April, 1985, K. Mitsuhashi et al. report preparation of 3-trifluoromethyl-5-hydroxyisoxazoles substituted with methoxycarbonyl or ethoxycarbonyl at 4-position. C. Baldoli et al., Gazz. Chem. Ital., 3, 347 (1981) disclose isoxazolin-5-ones substituted with phenyl or ethoxycarbonyl at 3-position, and with alkyl, phenyl or benzyl at 4-position. However, the 3-perfluoroalkyl,-5-hydroxyisoxazoles of the present invention have not been reported in the literature.